![]() For this instrument a temperature of 77.2 C is stored as (the integer) 772, why we use 1 decimal. The instrument stores the measured temperature in register 289. How to configure such a serial port is described on the pySerial page: įor example, consider an instrument (slave) with address number 1 to which we are to communicate via a serial port with the name /dev/ttyUSB1. The instrument is typically connected via a serial port, and a USB-to-serial adaptor should be used on most modern computers. This software has been tested using a Westermo MDW-45 RS232-to-RS485 converter. This has the advantage that the latter is galvanically isolated using opto-couplers, and has transient supression. There are direct USB-to-RS485 converters, but I use a USB-to-RS232 converter together with an industrial RS232-to-RS485 converter. To connect your computer to the RS485 bus, a serial port is required. ![]() The physical layer is most often the serial bus RS485, which is described at. In the Modbus RTU protocol, only the master can initiate communication. There can be several instruments (slaves, nodes) on a single bus, and the slaves have addresses in the range 1 to 247. For hardware details on these process controllers, see Eurotherm 3500 and Omega CN7500. Also a driver for Omega CN7500 is included. It uses the MinimalModbus Python module for its communication. MinimalModbus is intended for general communication using the Modbus RTU protocol (using a serial link), so there should be lots of applications.Īs an example on the usage of MinimialModbus, the driver I use for an Eurotherm 3504 process controller is included. These come with different types of communication protocols, but the controllers I prefer use the Modbus RTU protocol. The application for which I wrote this software is to read and write data from Eurotherm process controllers. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. Archives
January 2023
Categories |